Carine Patry Hoskins, who is married with two children and was a member of the inquiry team, began a relationship with David Sherborne, who has represented some phone hacking victims.

In a letter to Rob Wilson, a Conservative MP, Lord Justice Leveson for the first time provided a detailed breakdown of her role during the early stages of the inquiry into press standards, disclosing that she met, prepared and interviewed witnesses, reviewed their statements and researched the legal background.

Mr Wilson said that it was “completely inappropriate” for her to have played such an important role while developing such close personal relations with Mr Sherborne.

In August last year, four months before the end of the inquiry, the pair went on holiday to the Greek island of Santorini. They “discussed the possibility” of a future relationship but decided against it.

Miss Patry Hoskins was paid £218,606 for her work between July 2011 and November 2012.

Mr Wilson said: “It would be completely inappropriate for someone to carry out these important tasks for an impartial public inquiry while developing such close personal relations with one of the parties’ barristers to the point that they went on holiday together to contemplate an affair.

“I am very surprised that Lord Justice Leveson has not already taken the many opportunities available to him to make this clear.”

Lord Justice Leveson praised Miss Patry Hoskins for her work. He said: “[She] showed a real commitment to working towards the inquiry’s challenging timetable, worked to meet pressing deadlines and, as far as I am concerned, made a valuable contribution to the inquiry.”

He said that she had “no input” into the conclusions or recommendations of the report itself. “It is misleading to extrapolate from this later work and use it to define her overall contribution,” he added.

Earlier this year, Lord Justice Leveson dismissed the idea that his report could have been tainted by the alleged relationship. In a letter to Mr Wilson, he said Miss Patry Hoskins only carried out “proof reading” in the period after the two apparently become involved.

He insisted: “There was simply no room for a 'breach of confidence or other conspiracy’ as a result of personal relations between her and Mr Sherborne.”

Counsel’s fees for the inquiry were listed as £1.44 million and a further £315,600 was spent on barristers providing assistance to counsel.

Public hearings started on November 14, 2011, and the inquiry sat for 97 days.